At some point, you'll receive a phone call from Ashley, who will request that you go see Ray Boccino. Johnny doesn't care much for this mobster, but nonetheless, he agrees to head over to his restaurant to meet him. The restaurant in question is located at the southern end of Algonquin, on Denver Avenue. When you arrive, Johnny will have an interesting and awkward conversation with Ashley. When he heads on inside, Ray gives him the down-low on what he needs. Though it's pretty clear to him that Johnny doesn't like him, he asks him to move a couple million dollars worth of diamonds for him. Johnny agrees.

First things first -- Johnny will automatically call Jim once outside of the restaurant, requesting his help. Jim tells him that he'll hook him up with the Algonquin branch of the Lost, who will help on this. So first, you're going to have to head to a nearby location to meet up with these unknown bikers. They can be found to the southeast of Ray's restaurant, on Emerald Street. When you get near them, you'll realize they're already rolling, so simply get to the front of the caravan and begin moving towards Broker, where the diamonds are located.

Naturally, your GPS on your HUD will let you know exactly where you need to go, so there's little to worry about as far as direction. And since you're riding at the front of the group, the tempo of the ride will be up to you. Your destination is the heavily-winding road of Oakley Street, tucked in the southwest corner of the Dukes-Broker island, due north of Broker Bridge. When you arrive at the Broker Naval Yard and head to the predetermined location, get ready for a cutscene.

You'll witness the deal going down firsthand. The two sides exchange the goods for money after a mild dispute over the pricing. It seems these diamonds are too good to resist, which is a good thing in and of itself, since those diamonds will soon be changing hands. But as Johnny and his crew assemble and attempt to ambush the purchasers, they become privy to the situation, return fire, and scamper off. Obviously, it's going to be up to you to take care of them and reclaim the diamonds.

This is one hell of a car chase, and depending on the weaponry you do or don't have at the time you're asked to do this, this will be an easy or hard affair for you. You'll begin after the cutscene already on your bike, so all you have to do is drive forward and begin following the limousine, which is itself being tailed by a sedan full of armed thugs. You'll likely want to follow behind the latter car and deal with the armed thugs first, which will make things much, much easier for you. Of course, if you have explosives, like say a grenade, try cooking it just so and then launching it underneath the sedan to rid yourself of it quickly.

As for the limo, well, the passengers within are equally as dangerous, though you won't coerce them to return fire until the shooters in the back car have been eliminated. Pepper the car with gunfire to hopefully take out the driver (who is, by the way, the main target in both vehicles, since the car simply won't drive without its driver... duh.) With the destruction of the limousine comes an on-foot pursuit. Make sure you follow the proper person, the one holding the diamonds (marked by an arrow over his head, and on your HUD.) Once he's slain, be sure to pick up the diamonds that will show up on the ground next to his body.

With the diamonds in hand, the game will prompt you to place the diamonds in two trash bags. Astute GTAIV veterans will recognize this as a prologue to one of Niko's missions in the main quest, where Niko and company collect trash bags full of diamonds. Both drop offs are on the southern end of Algonquin, so getting to them (since the chase likely concluded in the same borough) shouldn't be an issue for you. The westernmost drop point is on Hematite Street. The easternmost drop point is on Emerald Street. Keep in mind that you'll encounter a car full of Ray's goons en route from the first point to the second point, but they are easily dealt with. The mission ends once the diamonds are dropped.